Cement additives

ABSTRACT

An additive for hydraulic cement comprises a major amount of sodium nitrite in admixture with a minor amount of calcium formate, optionally with triethanolamine or sodium benzoate.

AU 116 EX United States Patent 1191 Whitaker Apr. 2, 1974 CEMENT ADDITIVES 3,668,150 6/1972 Horvitz 106 90 3,329,517 7/1967 Dodson et a1 1 106/90 [751- Gnnvm' Heme 2,860,060 11/1958 Benedict et a1 106/90 Hempstead, England [73] Assignee: Fosroc A.G., Zug, Switzerland Primary Examiner-Delbert E. Gamz Assistant Examiner-James W. Hellwe e 22 F1 d: 1 10 1972 8 l l l C y Attorney, Agent, or FirmCaesar, Rivise, Bernstein 8L [21] Appl. No.: 270,358 Cohen [52] US. Cl. 106/90, 106/315 57 ABSTRACT [51] Int. Cl. C0411 7/02 58 Field of Search 106/90, 315, 314 addmve hydraul'c cement P a amount of in admixture with a minor [56] Rehnnces Cited amount of alcmfi igrmate, optionally with triethanol- UNITED STATES PATENTS amine or sodium benzoate.

3,210,207 10 1965 Dodson et al .1 106 90 6 13 Claims, No Drawings CEMENT xnnmvss BACKGROUND OF THE INVENTION cium silicate 3Ca O. Si02 and a minor amount of tricalcium aluminate 3CaO. A1203), is mixed with water, setting takes place in only a few hours. However the hardening of the cement takes much longer; in some cases final hardness is only achieved after weeks. The setting is due to the initial reaction of water with the tricalcium aluminate and the hardening is mainly due to the reaction of water with the tricalcium silicate. Ultimately, a gelatinous hydrated product, (probably gelatinous calcium silicate) forms and probably binds the particles together.

The rate of setting is dependant on the temperature, the setting reaction proceeding very slowly at lower temperatures. it is desirable to accelerate setting. As on-site heating is beset with difficulties, it is general practice to add to the water/hydraulic cement mix, a setting accelerator, which serves to decrease the setting time both at high and at low temperatures. Such accelerators includ rids, carbonates, hydroxides or rsilicates. Calcium chlone lS l chlori ems react with atmospheric moisture and oxygen to form an acidic mixture which will attack a metal reinforcement. Unless the reinforcement is completely sealed against the atmosphere it can, in time, be seriously corroded. Hence calcium chloride is not preferred for use with metal (especially steel) reinforced concrete.

SUMMARY OF THE INVENTION It is an object of the invention to provide an additive for a hydraulic cement usable with metal reinforcement.

It is an object of the invention to provide an additive for a hydraulic cement which can be used at low temperatures.

It is another object of the invention to provide an additive for hydraulic cement which is free of chloride.

It is yet another object of the invention to provide an additive for hydraulic cement which gives improved concrete compressive strength.

These and other objects of the invention are obtained using an additive which comprises a major amount of sodium nitrite in admixture with a minor amount of calcium formate. Optionally the additive may also contain a third constituent, for xample triethanolamine or sodium benzoate, e.g. in Tfia panremeb by weight.

A preferred dry additive comprises 19 to 48% calcium formate, 81 to 52% sodium nitrite, and 0.1% to 10% of triethanolamine or sodium benzoate. Water maybe added in a weight ratio of water to additive of up to 0.8:1, preferably 0.4 to 0.6 to form a liquid additive.

The additive may be admixed with the cement just before use on site or dry additive may be admixed with the cement in manufacture, and water added on site. Preferably the additive is dissolved in the gauging water (water used for admixture with the cement) which is then added to cement.

The additive may be added to the cementitious composition in amounts up to 20% by weight, preferably l6% by weight.

The following examples will serve to illustrate the invention. In these examples, use is made of two specific additives (parts are by weight) Additive A calcium formate 48% sodium nitrite 52% (Application rate 1.8 lb/cwt dry cement) Additive B The following test procedures were used in the Examples. Compressive strength was measured on a concrete containing by weight, one part test cement (Portland or sulphate-resisting) 2.4 parts sand and 3.6 parts inch to 3/16 inch Thames gravel, these being mixed according to British Standard BS I881. The 4 inch cubes for compressive strength determinations were cured under BS 12 conditions (i.e. 20 C) or immediately placed at +6 C and then cycled every 24 hours between +6 C and 6 C.

Water Reduction was determined by the following test. If the quantity of water required to give a control concrete a degree .of workability is l00%, the water content required by cement with admixture for the same workability expressed as a percentage of the control concrete water requirement is termed water reduction" (for example if without admixture 60 lbs of water is required, but with admixture only 54, water reduction is [(6054)/60] X 10%).

The Proctor Needle and Vicat tests to determine setting times were performed as described in ASTMC. 40.3 with 122:4 mortars and British Standard BS 12 with neat cement, respectively. The slump test was measured as described in British Standard BS 1881 and BS 12.

EXAMPLE I Samples of ordinary Portland cement and sulphateresisting cement were made up into a concrete as indicated, with and without the additives as indicated in Table l. The products were cured at 20 C. and measured and the results are shown in Tables I and ll below.

The results of Tables I and ll show that both additives give a much higher compressive strength in all stages of setting and hardening than the control.

TABLE 1 Sample Water/ Slump Water Density Compressive Strength (p.s.i.)

Cement (ins.) Reduction (1b/cu.ft.) 18hr hr 24hr 3day 7day Ratio Ordinary Portland Cement Control 0.625 1% 146.2 730 970 1540 2660 3750 Additive B (1.2 lbs/cwt) Cement 0.625 1% 146.2 1470 1760 1680 3470 4060 Additive A (1% lb/cwt) 0.625 1% 146.9 1270 1260 1820 3440 4800 Control 0.625 2% 148.6 1050 1190 1680 2730 3850 Additive B (2.4 lb/cwt) 0.605 1% 3.2 148.1 1820 2100 2500 3640 4740 Additive A (3 lb/cwt) 0.600 2% 4.0 147.7 1470 1540 1970 2450 4070 Sulphate resisting Cement Control 0.610 2 147.0 670 980 1150 3080 3550 Additive B (1.2 lb/cwt cement) 0.605 2% 0.8 145.0 900 1060 1400 3470 4190 Additive A (lllb/cwt) 0.559 2% 1.8 146.0 830 870 1370 3080 4170 Control 0.591 1% 147.7 700 1120 1050 2370 3640 Additive B (2.4 lb/cwt cement) 0.575 1% 2.7 146.4 1470 1750 1890 3500 5020 Additive A (3 lb/cwt) 0.545 2% 7.8 147/1 1330 1680 1960 3500 4970 TABLE 11 T Compressive strength (p.s.i.) Water/ Water cement Slump redttc- Densitg 18 20 24 3 7 Smple ratio (ins) tton (lbJcu. It. hrs. hrs. hrs. days days Control O. 685 2% 147.1 60 60 60 110 630 Additive B (1.21lt)D.//cwt. cement). gag gi/g 228 l A l cwt. giiiio liuf 0. 691 1% 980 2' 430 phate resisting cement. Additive B (2.4 lb./t.wt. cemen 0. 576 1% 2. 7 1,340 3, 220 Additive A (3 lb./cwt.) 0. 5415 7.8 1,630 3,640

0. 625 310 770 0. 603 1, 310 1, 820 g: 1 Egg Ordinary portland cement. Additive B lcwt 0.003 y 60 Additive A (3lb./cwt.)... 0.600 1, 3, 90

EXAMPLE I] A series of tests were set up to test the efficiency of additive B at various addition rates and temperatures.

The samples were tested by measurement of the Proctor Needle Setting times on two samples of 1:2.4 mortars (sulphate resisting and ordinary Portland cement). The results are given in Tables Ill and IV.

EXAMPLE 111 A further set of comparative tests was set up under various conditions using the following:

Additive C comprised 75% calcium formate, 25% sodium nitrite Additive D comprised 48% calcium formate, 52% sodium nitrite Additive E comprised 25% calcium formate, 75% so- EXAMPLE IV The compressive setting time of the compositions of Example 111 was determined on Portland Cement, the samples being cured at 20 C. The Vicat and Proctor Needle determinations in minutes are shown in Table V1.

From the results of the Tables, it is clear that additives of this invention give positive strength increases and acceleration of setting times over the controls and compare favourably with CaCl, with regard to strength and setting times.

Further tests have shown that the resultant concretes show no negative results with regard to shrinkage and dipmnitritq V V V w m r v I sulphate resistance, and have a positive corrosion inhi- The cement used was ordinary Portland cement. bition efi'ect.

TABLE 111 Using Portland Cement Rate of Temperature Water/ Sample Addition (C) Cement Setting Times(hrs) Ratio lnitial Final Control 20 0.408 3.1 5.0 Additive B 1.2 lb 20 0.406 2.5 3.7 Additive A 1% lb 20 0.407 2.7 4.0

Control 20 0.415 3.3 5.1 Additive B 2.4 lb 20 0.393 2.4 3.3 Additive A 3 lb 20 0.422 2.4 3.5

Control 6 0.455 6.5 10.6 Additive B 1.2 lb 6 0.400 3.8 6.0 Additive A 1% lb 6 0.410 3.9 6.5

Control 6 0.400 5.0 10.0 Additive B 2.4 lb 6 0.400 3.0 6.2 Additive A 3 lb 6 0.400 3.0 6.3

. TABLE 1V Using Sulphate resisting Cement Rate of Temperature Water] Setting Times (hrs) Sample Addition Cement Initial Final ("C) Ratio Control 0.397 4.8 6.8 Additive B 1.2 20 0.403 4.7 6.5 Additive A l 20 0.305 4.0 5.5

Control 20 0.393 4.7 6.3 Additive B 2.4 20 0.393 4.2 5.7

Control 6 0.395 I l Additive B 1.2 6 0.375 8 Additive A 1% 6 0.375 8 Control 6 0.40 l0.8 l9 Additive B 2.4 6 0.40 6.2 l 1.3 Additive A 3 6 0.40 4.0 0.0

These results shovv that the additives decrease the 20 ing current or future knowledge, readily adapt the same setting time of both Portland Cement and sulphatefor use under various conditions of service. resisting cement. I claim:

g g WTIEFT H .Comp. Strength .s.i.)

Sample Curing W/C Slump Ref. Conds. Ratio (ins) lday 3 D ay 7day 28day Control 5C last 0718 2% 840 750 700 g 24 hrs in Water at l9C 2% Mix C 0.679 2% 830 690 570 2% Mix D 0.680 2% 1130 770 870 2% Mix 5 0.670 2% 850 1000 2% CaCl, 0.660 2 1110 880 740 Flake Control Cured 0.680 2 I 2040 3520 outdoors 2% Mix D Max.Temp 0.670 2 630 3080 5270 11C 2% CaCl, Min. Temp 0.603 2 720 3160 5030 3C Flake Mean Temp Control 13s.12 0.676 2 1130 3840 5030 (Std. 2% Mix D Lab. 0.660 2 1730 5040 6340 Cond'ns.) 2% cacl, 0.610 2 1550 4590 5950 Flake Control 13s.12 0.673 2 1260 4240 5840 (Std. I 1% Mix 1) Lab. 0.640 2 1750 4690 6250 Condns.) 1% Mix E 0.640 2 1620 4790 6080 1% CaCl, 0.646 2 1780 4990 6210 Flake TABLE VI Vicat Proctor Needle Sample Initial Set Final Set lnitial Set Final Set Control 115 I 310 430 2% Mix c 2% Mix D 75 120 170 290 2% Mix E 65 115 2% CaCl, Flake 55 90 250 Control 140 220 310 430 ix D V 115 M 165 220 300 1% Mix E 14 220 280 1% c661, Flake 80 105 250 Without further elaboration, the foregoing will so 1. An additive for use in hydraulic cements, comprisfully illustrate my invention that others may, by applying a major amount of sodium nitrite in admixture with my I a minor amount of calcium formate, said major amount of sodium nitrite comprising about 52% to 81% by weight of said additive and said minor amount of calcium formate comprising about l9% to 48% by weight of said additive.

2. An additive according to claim 1, which also contains triethanolamine or sodium benzoate.

3. An additive according to claim 2, wherein the triethanolamine or sodium benzoate is present in a proportion of up to 40% by weight of the additive.

4. An additive according to claim 2 wherein the triethanolamine or sodium benzoate comprises about 0.1 to 10% by weight of said additive.

5. An additive according to claim 1 and water.

6. An additive according to claim in which the weight ratio of water to additive is in the range of 4:1 to l:9.

7. An additive according to claim 6 wherein the weight ratio of water to additive is in the range 2:3 to 3:2.

8. An additive according to claim 1, and a dispersant to present the additive in liquid, paste or powder form.

9. An additive according to claim 1 comprising about 48% calcium formate, and about 52% sodium nitrite.

10. An additive according to claim 2 comprising about 19.5% calcium formate, about 77.9% sodium nitrite, and about 2.6% triethanolamine.

11. A cementitious composition incorporating an additive according to claim 1.

12. A cementitious composition according to claim 11, in which the weight of additive in the composition is up to about 20%.

13. A cementitious composition according to claim 12, in which the weight of additive in the composition is about 1% to about 6%.

t it i I 

2. An additive according to claim 1, which also contains triethanolamine or sodium benzoate.
 3. An additive according to claim 2, wherein the triethanolamine or sodium benzoate is present in a proportion of up to 40% by weight of the additive.
 4. An additive according to claim 2 wherein the triethanolamine or sodium benzoate comprises about 0.1 to 10% by weight of said additive.
 5. An additive according to claim 1 and water.
 6. An additive according to claim 5 in which the weight ratio of water to additive is in the range of 4:1 to 1:9.
 7. An additive according to claim 6 wherein the weight ratio of water to additive is in the range 2:3 to 3:2.
 8. An additive according to claim 1, and a dispersant to present the additive in liquid, paste or powder form.
 9. An additive according to claim 1 comprising about 48% calcium formate, and about 52% sodium nitrite.
 10. An additive according to claim 2 comprising about 19.5% calcium formate, about 77.9% sodium nitrite, and about 2.6% triethanolamine.
 11. A cementitious composition incorporating an additive according to claim
 1. 12. A cementitious composition according to claim 11, in which the weight of additive in the composition is up to about 20%.
 13. A cementitious composition according to claim 12, in which the weight of additive in the composition is about 1% to about 6%. 